NorovirusEssential Information

Norovirus

OriginsNoroviruses were first identified as the cause of a gastroenteritis outbreak in 1968 in Norwalk Ohio in the US. They are a group of small non-enveloped viruses which are highly contagious and are believed to be the most common cause of acute gastroenteritis and cause outbreaks in both healthcare and community settings. These viruses are single strand RNA viruses from the family Caliciviridae. Norovirus is classified in five genotypes with genotype GI and GII causing most of the human norovirus infections.

In the US it is estimated that norovirus causes 21 million cases of gastroenteritis each year, which is approximately 60% of all acute gastroenteritis cases, but only 570-800 deaths, so it is rarely fatal. A 2009 study by the CDC concluded that 40% of all foodborne illness outbreaks in the US were caused by Caliciviruses/norovirus.

Norovirus infections are seen in all age groups, with the elderly having the most severe outcomes and longer duration of illness. There are no known animal sources for norovirus infections. Immunity after recovery is specific to the strain acquired and appears to only exist for a few weeks after recovery. There are no vaccines available to prevent infection.

While in developed countries, patients with acute gastroenteritis may be tested for norovirus, the test is relatively expensive, which prevents routine testing in many developing countries. Thus the global scope of norovirus infections is not currently known. Also, since many people infected with norovirus only develop minor symptoms, many outbreaks may go undetected or unreported.

Norovirus is relatively stable in the environment and believed to be capable of surviving for 2-3 weeks outside the body. Outbreaks may be most common in Healthcare facilities (including nursing homes and hospitals) but are associated with a wide range of facilities including foodservice, cruise ships, schools, child-care centers, and hotels. Outbreaks happen predominantly in the winter months (Nov to Apr in the Northern hemisphere.) Outbreaks in the US are believed to have predominantly (~70%) been caused by infected food handlers contaminating food.

DiagnosisTransmission of norovirus usually occurs through fecal-oral routes, with a 12-48 hour incubation period before symptoms occur. Norovirus can be detected in feces before other symptoms are present and symptoms include the following and typically persist for 2-5 days.

• Nausea and vomiting• Diarrhea• Fever• Headache• Cramping, body aches, and malaise

Norovirus causes inflammation (swelling) of the stomach and/or intestines, which causes abdominal pain. Many of the symptoms likely to present in the illness are often seen in patients with other common gastrointestinal diseases. Diagnosis and treatment should only be performed by a trained physician who can rule out other potential diseases.

The virus can be found in feces for 2-4 weeks or more after recovery. Norovirus shedding peaks at 2-5 days after infection at a rate of 100 billion viral particles per gram of feces. Up to 30% of norovirus infections are asymptomatic, with the asymptomatic person shedding the virus, likely contributing to the spread of the disease.

Method of TransmissionFood and water are easily contaminated by norovirus, but the contamination is generally caused by breaches in personal hygiene by food handlers or through contaminated water sources that are used to grow/cultivate food. Small doses (10-100 viral particles) are believed to be capable of causing infection.

Norovirus can spread rapidly through confined populations because of these factors:

• Ease of transmission• Low infectious dose• Short incubation period• Environmental persistence• Lack of durable immunity after infection• Continued shedding of the virus after symptoms have

resolved

Food preparation surfaces, other environmental surfaces and Healthcare patient care equipment that can be contaminated by vomit or feces can be a potential source of infection. Once surfaces are contaminated with norovirus, workers may contaminate their hands by touching contaminated surfaces, and then touch an uninfected person or that person’s environment. If the uninfected person contaminates their hands and then touches their mouth, they can become infected. Vomiting can cause droplets contaminated with norovirus to be swallowed by uninfected persons, causing infection.

PreventionTransmission Based Precautions: When a person infected with norovirus is being treated in a hospital, they will generally be put into a single patient room to help protect the healthcare staff, other patients, and visitors. Healthcare workers entering the patient’s room will observe contact precautions in addition to standard precautions. This includes wearing a gown and gloves, performing hand hygiene on room entry and exit and before/after glove use. If the patient is vomiting or there is the risk of splashing to the face, droplet precautions (surgical mask and eye protection or face shield) should also be observed.

Contact precautions should be used for the duration of the diarrhea and for 48 hours after it resolves. If a patient presents with diarrhea, they should proactively be placed in contact isolation until testing confirms the source of the infection.

The decision to have visitors also follow contact precautions is an unresolved issue as the benefit of this practice is thus far unproven. At a minimum, visitors should perform hand hygiene upon room entry and exit and minimize contact with other patients to reduce the risk of transmission.

To avoid exposure to norovirus outside Healthcare, avoid contact with vomitus or diarrhea. If exposure occurs, wash hands and change clothing immediately after exposure.

Hand Hygiene: Proper hand hygiene by staff, patients, and visitors, is one of the main ways to prevent transmission of norovirus. In Healthcare, while the use of alcohol hand rubs is always acceptable on patient room entry, on patient room exit, hand washing with

soap and water is preferred in many guidelines, including the CDC recommendations, because of variable effectiveness of alcohol hand rubs against small non-enveloped viruses such as norovirus.

Food handlers: For food handlers, regular hand hygiene is required to prevent food related outbreaks. Food handlers must perform hand hygiene prior to contact with or the preparation of food or beverages. Food handlers (people who work with, prepare or distribute food) must

be excluded from work if they develop symptoms of acute gastroenteritis.

Reduce Risk for Healthy People: If a patient in a hospital has diarrhea, they should be put in a single patient room with their own toilet or cohorted with other patients with norovirus. Only the patient should use the patient’s bathroom. Visitors should use public toilets. If around

a patient with diarrhea, staff and visitors should avoiding touching their eyes, nose, and mouth as this can help prevent acquisition of the virus.

Surface Cleaning/Disinfection: Norovirus has been found on environmental surfaces inside and outside Healthcare environments. Thorough environmental cleaning and disinfection of commonly touched environmental surfaces (door handles, toilet flush handles, light switches, elevator buttons,

keyboards, phone, etc.) with a cleaner/disinfectant capable of killing norovirus is important to reduce the risk posed by environmental surfaces or patient care equipment. Cleaning compliance should also be assessed as this affects the effectiveness of environmental hygiene efforts.

Increasing the frequency of cleaning/disinfection is recommended during outbreaks. For Healthcare facilities, increase ward/unit cleaning to twice daily and frequently touched surfaces to three times daily may also help interrupt and outbreak.

Food handling/processing equipment that is contaminated with vomitus or contaminated food should be washed and sanitized/disinfected before reuse, preferably in a commercial dishmachine. Dishware for a patient infected with norovirus should be handled using standard precautions, but can be washed in the normal manner. Normal cooking will inactivate norovirus, but food known to be contaminated with norovirus should be discarded.

Fabric Handling ensuring soiled fabric from norovirus patients is handed in a way to prevent transmission (i.e. minimize agitation), using standard precautions. Healthcare laundering procedures for contaminated fabric are capable of making the fabric hygienic.Good Health Practices: Practicing good health is also helpful in preventing the development of many illnesses. The strength of a person’s immune system is often related to their overall health. Get plenty of sleep, eat healthy, be physically active, manage stress, and drink plenty of fluids to keep your immune system strong.

Much of the Information used in the development of this brochure was taken from the sites listed below.

If you have any questions, please contact Diversey Customer Service at your local number. Much of the Information used in the development of this brochure was taken from the sites listed below:

http://www.cdc.gov/hand-foot-mouth/index.html

http://www.wpro.who.int/emerging_diseases/documents/HFMDGuidance/en/

http://www.wpro.who.int/mediacentre/factsheets/fs_10072012_HFMD/en/

References and useful websites

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